1. Field of the Invention
The present invention relates to a mobile communication system and, more particularly, to a network-initiated area event triggered positioning method for a roaming terminal in a session-based position information system.
2. Description of the Related Art
In a mobile communication system a function part for calculating a position of a terminal is included in a mobile communication network to provide a location service for transferring a location of a terminal to a certain entity periodically or is according to a user request. A network structure related to the location service varies depending on an internal network structure such as 3GPP or 3GPP2, etc.
Methods for calculating the position of the terminal in the mobile communication system include a cell-ID method in which an id of a cell to which the terminal belongs is transferred, a method in which time taken for radiowaves to arrive at each base station from the terminal is measured and then the position of the terminal is calculated by using triangulation, and a method using GPS.
In order to provide the location service to a user by using the position calculating methods, considerable signaling and position information should be transferred between the mobile terminal and a position server. Thus, recently, standardized positioning technologies for providing the location service, namely, the location services based on the position of the mobile terminal, are widely adopted. The positioning technologies can be provided through a user plane and a control plane, and the SUPL (Secure User Plane Location) that provides the location service through the user plane is a typical example of the technologies.
The SUPL, which is effective for transferring position information required for calculating the position of the mobile terminal, transfers position assistance information such as GPS assistance and uses a user plane data bearer in order to transport positioning technology-related protocols between the mobile terminal and the network.
In general, in the position information system, a location service-related SUPL network includes a SUPL agent, an SLP (SUPL Location Platform) and an SET (SUPL Enabled Terminal). The SUPL agent indicates a logical service access point that uses actually measured position information, and the SLP indicates an SUPL service access point of the network that accesses network resources to obtain position information.
The SET is a device that communicates with the SUPL network using the SUPL interface, which can be, for example, a UE (User Equipment) of a UMTS, an MS (Mobile Station) of GSM, an IS-95 MS, or a laptop computer or a PDA having the SET function. The SET can be also various other types of mobile terminals that are connected through a WLAN.
The SET supports procedures defined in the SUPL by interworking with the network through the user plane bearer. In this case, the network to which the user had initially registered may be called a home network, and the network of an area where the user moves into from the home network area may be called a visited network. An SLP of the home network may be called an H-SLP (Home-SLP) and an SLP of the visited network may be called a V-SLP (Visited-SLP). When the SUPL procedure starts in the network, an SLP to which an external client is first connected may be called an R-SLP (Requesting SLP). The R-SLP can be a logical entity which is the same as the H-SLP or not. The SET for current positioning can be defined as the target SET.
The SLP, a network element, includes an SPC (SUPL Positioning Center) that calculates an actual location and an SLC (SUPL Location Center) that performs other roles of the SLP that calculates the position information, namely, roaming and resource management, etc. Thus, the SET may calculate the position information through communication with the SPC via the SLC (proxy mode) or calculate the position information by being immediately connected with the SPC (non-proxy mode).
However, although the related art provides the immediate positioning method based on the SUPL, it fails to propose area-based, area-related or area event triggered positioning for the SUPL-based roaming terminal.